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Day 3 follicle stimulating
hormone: FSH
Follicle stimulating hormone (FSH) is
one of the most important hormones involved in the natural menstrual cycle as well as in
pharmacological (drug-induced) stimulation of the ovaries. It is the main hormone involved
in producing mature eggs.
FSH is the same hormone that is
contained in the injectable gonadotropins which are used to produce multiple eggs for
infertility treatment.
When a women goes into menopause she
is essentially running out of eggs in her ovaries. The brain senses that there is a low
estrogen environment and more FSH is released from the pituitary gland in an attempt to
stimulate the ovaries enough to produce a good follicle and estrogen.
You can think of it like
stepping on the gas pedal in the car to get going. The FSH is the gas, and the
pituitary gland releases FSH to get a follicle "going" at the
beginning of every menstrual cycle. If there are less follicles left (and
perhaps lower quality follicles) the "gas" has to be increased to get
a follicle to start developing. In a menopausal woman, the gas pedal is on the
floor for the rest of her life - even though there are no follicles (or eggs)
left that are capable of developing, the woman's body never gives up trying and
FSH levels are permanently elevated.
Women in menopause usually have FSH
levels that are above 40 mIU/ml. As women approach menopause their baseline FSH levels
(day 3 of their cycle) will tend to gradually increase over the years. When they run out
of follicles capable of responding, their FSH will be quite high (over 30-40 mIU/ml) and they will stop
having menstrual periods.
By measuring a baseline FSH on day 3
of the cycle (we do it on either day 2, 3, or 4), we can often get an indication that the women is closer to menopause and
has relatively less "ovarian reserve". Another way of saying this is that if the
baseline FSH is elevated the ovarian reserve (how many eggs are left) is reduced
and sometimes also the egg quality is reduced. In other words, an
elevated FSH represents a reduced egg supply (in numbers of eggs remaining) and
it might also reflect a
compromise of egg quality. However, in general, the best quick and easy
"test" for egg quality is looking at the woman's drivers
license - her age.
There are some practical problems
associated with this test:
1. The cut off values used to say that
egg quantity is good, ok, or poor is very laboratory dependent. What this means is that a
given level of, for example, 12 in one laboratory may reflect good ovarian
reserve and egg quantity - whereas the same level in another laboratory using a different
assay may reflect poor ovarian reserve, poor egg quantity, and low live birth
rates with IVF. See below for more on interpretation of results.
2. While an abnormal result (high
baseline FSH) tends to be very predictive of poor egg quantity and quality, a normal result does not
necessarily mean that the egg quantity and quality is good. There are a significant number of women
with normal baseline FSH values that do have poor egg quantity and quality that is not being reflected
in their FSH value.
This is particularly true for women in
their 40s. An infertile 44 year old woman with a normal FSH (for example 6) still has a
very low probability of conceiving and delivering with in vitro fertilization - or with
any other fertility treatment. The fact that she is 44 greatly diminishes her chances -
even if her FSH is normal. This is why IVF programs have age cutoffs. The oldest women
accepted by IVF programs varies somewhat - most programs have a cutoff somewhere
between age 42-45. Infertile women older than this will rarely be successful using their
own eggs. However, women in their 40s are
excellent candidates for in vitro fertilization with donor eggs.
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